1. Field of the Invention
This invention relates to a wireless power supplying system of the non-contacting power supplying type capable of carrying out supplying and reception of power in a non-contacting or wireless fashion.
2. Description of the Related Art
An electromagnetic induction method is known as a method for carrying out supplying of power in a wireless state.
Further, in recent years, attention is paid to a wireless power supplying system and a charging system which uses a method called magnetic field resonance method which utilizes an electromagnetic resonance phenomenon.
In a contactless power supplying system of the electromagnetic induction type which is used most widely at present, it is necessary for a power supply source and a power supply destination, which is the power reception side, to commonly use magnetic fluxes. Therefore, in order to transmit power efficiently, it is necessary to dispose the power supply source and the power supply destination very closely to each other, and also alignment for coupling is significant.
Meanwhile, a contactless power supply system which utilizes an electromagnetic resonance phenomenon is advantageous in that, from the principle of the electromagnetic resonance phenomenon, power can be transmitted over a greater distance than that by the electromagnetic induction system and besides, even if the alignment is somewhat rough, the transmission efficiency does not drop very much.
It is to be noted that, as the electromagnetic resonance phenomenon, not only magnetic field resonance but also electric field resonance are available.
For example, Japanese Patent Laid-Open No. 2001-185939 (hereinafter described as Patent Document 1) discloses a wireless power supplying system which adopts the magnetic field resonance method.
In the technique disclosed in Patent Document 1, power is transmitted from a power supplying coil connected to a power supplying circuit to a resonance coil, also called consonance coil, by electromagnetic induction. Further, modulation of the frequency is carried out a capacitor connected to the resonance coil.
In recent years, a wireless power transmission technique has been reported which achieves transmission of power of 60 W over a distance of 2 m by adopting the magnetic field resonance system which utilizes a resonance phenomenon of a magnetic field.
Also development of a “wireless power supply system” of a high efficiency has been reported which transmits power of 60 W to drive an electronic apparatus at a place spaced by 50 cm by adopting the magnetic field resonance system.